/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef SKY_ENGINE_WTF_TEMPORARYCHANGE_H_
#define SKY_ENGINE_WTF_TEMPORARYCHANGE_H_

#include "flutter/sky/engine/wtf/Noncopyable.h"

namespace WTF {

// TemporaryChange<> is useful for setting a variable to a new value only within
// a particular scope. An TemporaryChange<> object changes a variable to its
// original value upon destruction, making it an alternative to writing "var =
// false;" or "var = oldVal;" at all of a block's exit points.
//
// This should be obvious, but note that an TemporaryChange<> instance should
// have a shorter lifetime than its scopedVariable, to prevent invalid memory
// writes when the TemporaryChange<> object is destroyed.

template <typename T>
class TemporaryChange {
  WTF_MAKE_NONCOPYABLE(TemporaryChange);

 public:
  TemporaryChange(T& scopedVariable, T newValue)
      : m_scopedVariable(scopedVariable), m_originalValue(scopedVariable) {
    m_scopedVariable = newValue;
  }

  ~TemporaryChange() { m_scopedVariable = m_originalValue; }

 private:
  T& m_scopedVariable;
  T m_originalValue;
};

}  // namespace WTF

using WTF::TemporaryChange;

#endif  // SKY_ENGINE_WTF_TEMPORARYCHANGE_H_
